The term "structural shape" is used herein to describe rod or bar-like structural material, generally of metal, of a variety of cross sections chosen to give various structural characteristics to the stock. Structural shapes include angles, I-beams, H-beams and channels, as well as round or polygonal cross section rod stock and flat bar stock which can be of rectangular cross ssction. These structural shapes are also known as profile, rod and bar steels or irons and generally the terms are used interchangeably at least when applied to steel structural members. They will be so used interchangeably hereinafter and thus any reference to profile steel and/or bar or rod steel and/or flat steel or flat bar steel or stock will be understood to refer to the structural shapes as above described.
It is known to provide shears, frequently referred to as power shears in which a slide carrying a movable blade is driven by hydraulic ram or some other power source and is equipped with means for severing different shapes and thus having associated blade arrangements oriented to accommodate the specific shapes.
In the past, however, the apparatus if it was capable of shearing different shapes without replacement of the blade assemblies, provided the blade assemblies one above another or were required to be of excessive width to accommodate the blade assemblies on a common horizontal plane.
A third alternative, of course, was to replace the working plate assembly for each different type of structural shape or stock cross section.
These systems had various disadvantages. For example, when the blade assemblies were vertically spaced, the different shapes had to be fed at different levels and the cut pieces were recovered at different levels. This made feeding a problem and, in addition, caused problems when the shear was associated with a punch or some other machine for acting upon the cut pieces.
It has already been mentioned that positioning a number of blade assemblies in the same plane but in horizontally spaced relationship gives rise to an excessive width of the machine which prevents it from being accommodated conveniently at a work site.
Finally, systems using replaceable blade assemblies and which require switchover for different structural shapes are complex and time-consuming to use since modification of the blade mounting may be required for blade replacement in switching over between one structural shape and another.